Intravesical BCG in patients with non-muscle invasive bladder cancer induces trained immunity and decreases respiratory infections

BACKGROUND

BCG is recommended as intravesical immunotherapy to reduce the risk of tumor recurrence in patients with non-muscle invasive bladder cancer (NMIBC). Currently, it is unknown whether intravesical BCG application induces trained immunity.

METHODS

The aim of this research was to determine whether BCG immunotherapy induces trained immunity in NMIBC patients. We conducted a prospective observational cohort study in 17 NMIBC patients scheduled for BCG therapy and measured trained immunity parameters at 9 time points before and during a 1-year BCG maintenance regimen. Ex vivo cytokine production by peripheral blood mononuclear cells, epigenetic modifications, and changes in the monocyte transcriptome were measured. The frequency of respiratory infections was investigated in two larger cohorts of BCG-treated and non-BCG treated NMIBC patients as a surrogate measurement of trained immunity. Gene-based association analysis of genetic variants in candidate trained immunity genes and their association with recurrence-free survival and progression-free survival after BCG therapy was performed to investigate the hypothesized link between trained immunity and clinical response.

RESULTS

We found that intravesical BCG does induce trained immunity based on an increased production of TNF and IL-1β after heterologous ex vivo stimulation of circulating monocytes 6-12 weeks after intravesical BCG treatment; and a 37% decreased risk (OR 0.63 (95% CI 0.40 to 1.01)) for respiratory infections in BCG-treated versus non-BCG-treated NMIBC patients. An epigenomics approach combining chromatin immuno precipitation-sequencing and RNA-sequencing with in vitro trained immunity experiments identified enhanced inflammasome activity in BCG-treated individuals. Finally, germline variation in genes that affect trained immunity was associated with recurrence and progression after BCG therapy in NMIBC.

CONCLUSION

We conclude that BCG immunotherapy induces trained immunity in NMIBC patients and this may account for the protective effects against respiratory infections. The data of our gene-based association analysis suggest that a link between trained immunity and oncological outcome may exist. Future studies should further investigate how trained immunity affects the antitumor immune responses in BCG-treated NMIBC patients.

Immune modulatory effects of progesterone on oxLDL-induced trained immunity in monocytes

Atherosclerotic cardiovascular diseases (CVD) are among the leading causes of death in the world. Monocyte‐derived macrophages are key players in the pathophysiology of atherosclerosis. Innate immune memory following exposure of monocytes to atherogenic compounds, such as oxidized low‐density lipoproteins (oxLDL), termed trained immunity, can contribute to atherogenesis. The current study aimed to elucidate intracellular mechanisms of oxLDL‐induced trained immunity. Using untargeted intracellular metabolomics in isolated human primary monocytes, we show that oxLDL‐induced trained immunity results in alterations in the balance of intracellular steroid hormones in monocytes. This was reflected by a decrease in extracellular progesterone concentrations following LPS stimulation. To understand the potential effects of steroid hormones on trained immunity, monocytes were costimulated with oxLDL and the steroid hormones progesterone, hydrocortisone, dexamethasone, β‐estradiol, and dihydrotestosterone. Progesterone showed a unique ability to attenuate the enhanced TNFα and IL‐6 production following oxLDL‐induced trained immunity. Single nucleotide polymorphisms in the nuclear glucocorticoid, progesterone, and mineralocorticoid receptor were shown to correlate with ex vivo oxLDL‐induced trained immunity in 243 healthy volunteers. Pharmacologic inhibition experiments revealed that progesterone exerts the suppression of TNFα in trained immunity via the nuclear glucocorticoid and mineralocorticoid receptors. Our data show that progesterone has a unique ability to suppress oxLDL‐induced trained immunity. We hypothesize that this effect might contribute to the lower incidence of CVD in premenopausal women.

An integrative genomics approach identifies KDM4 as a modulator of trained immunity

Innate immune cells are able to build memory characteristics via a process termed “trained immunity.” Host factors that influence the magnitude of the individual trained immunity response remain largely unknown. Using an integrative genomics approach, our study aimed to prioritize and understand the role of specific genes in trained immunity responses. In vitro‐induced trained immunity responses were assessed in two independent population‐based cohorts of healthy individuals, the 300 Bacillus Calmette‐Guérin (300BCG; n = 267) and 200 Functional Genomics (200FG; n = 110) cohorts from the Human Functional Genomics Project. Genetic loci that influence cytokine responses upon trained immunity were identified by conducting a meta‐analysis of QTLs identified in the 300BCG and 200FG cohorts. From the identified QTL loci, we functionally validated the role of PI3K‐Akt signaling pathway and two genes that belong to the family of Siglec receptors (Siglec‐5 and Siglec‐14). Furthermore, we identified the H3K9 histone demethylases of the KDM4 family as major regulators of trained immunity responses. These data pinpoint an important role of metabolic and epigenetic processes in the regulation of trained immunity responses, and these findings may open new avenues for vaccine design and therapeutic interventions.

The role of sirtuin 1 on the induction of trained immunity

Sirtuin 1 (SIRT1) has been described to modify immune responses by modulation of gene transcription. As transcriptional reprogramming is the molecular substrate of trained immunity, a de facto innate immune memory, we investigated the role of SIRT1 in the induction of trained immunity. We identified various SIRT1 genetic single nucleotide polymorphisms affecting innate and adaptive cytokine production of human peripheral blood mononuclear cells (PBMCs) in response to various stimuli on the one hand, and in vitro induction of trained immunity on the other hand. Furthermore, inhibition of SIRT1 upregulated pro-inflammatory innate cytokine production upon stimulation of PBMCs. However, inhibition of SIRT1 in vitro had no effect on cytokine responses upon induction of trained immunity, while activation of SIRT1 mildly modified trained immunity responses. In conclusion, SIRT1 modifies innate cytokine production by PBMCs in response to various microbes, but has only a secondary role for BCG and β-glucan-induced trained immunity responses.

The Set7 Lysine Methyltransferase Regulates Plasticity in Oxidative Phosphorylation Necessary for Trained Immunity Induced by β-Glucan

Trained immunity confers a sustained augmented response of innate immune cells to a secondary challenge, via a process dependent on metabolic and transcriptional reprogramming. Because of its previous associations with metabolic and transcriptional memory, as well as the importance of H3 histone lysine 4 monomethylation (H3K4me1) to innate immune memory, we hypothesize that the Set7 methyltransferase has an important role in trained immunity induced by β-glucan. Using pharmacological studies of human primary monocytes, we identify trained immunity-specific immunometabolic pathways regulated by Set7, including a previously unreported H3K4me1-dependent plasticity in the induction of oxidative phosphorylation. Recapitulation of β-glucan training in vivo additionally identifies Set7-dependent changes in gene expression previously associated with the modulation of myelopoiesis progenitors in trained immunity. By revealing Set7 as a key regulator of trained immunity, these findings provide mechanistic insight into sustained metabolic changes and underscore the importance of characterizing regulatory circuits of innate immune memory.

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Set7 regulates enhanced cytokine production in trained immunity in vitro

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Set7 knockout mice are unable to mount trained immunity against endotoxin challenge

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Set7 modulates cellular respiration in β-glucan-trained macrophages

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Set7-dependent histone methylation regulates MDH2 and SDHB in trained cells

In vitro induction of trained immunity in adherent human monocytes

A growing number of studies show that innate immune cells can undergo functional reprogramming, facilitating a faster and enhanced response to heterologous secondary stimuli. This concept has been termed “trained immunity.” We outline here a protocol to recapitulate this in vitro using adherent monocytes from consecutive isolation of peripheral blood mononuclear cells. The induction of trained immunity and the associated functional reprogramming of monocytes is described in detail using β-glucan (from Candida albicans) and Bacillus Calmette-Guérin as examples.

For complete details on the use and execution of this protocol, please refer to Repnik et al. (2003) and Bekkering et al. (2016).

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Isolation of PBMCs and monocytes using discontinuous density gradients

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In vitro induction of trained immunity in adherent monocytes

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Induction of trained immunity is assessed by cytokine production levels

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Generally applicable to test multiple stimuli and pharmacological compounds

Lysine methyltransferase G9a is an important modulator of trained immunity

Objectives

Histone methyltransferase G9a, also known as Euchromatic Histone Lysine Methyltransferase 2 (EHMT2), mediates H3K9 methylation which is associated with transcriptional repression. It possesses immunomodulatory effects and is overexpressed in multiple types of cancer. In this study, we investigated the role of G9a in the induction of trained immunity, a de facto innate immune memory, and its effects in non‐muscle‐invasive bladder cancer (NMIBC) patients treated with intravesical Bacillus Calmette‐Guérin (BCG).

Methods

EHMT2 expression was assessed upon induction of trained immunity by RNA sequencing and Western blotting. G9a inhibitor BIX‐01294 was used to investigate the effect on trained immunity responses in vitro. Subsequent cytokine production was measured by ELISA, epigenetic modifications were measured by ChIP‐qPCR, Seahorse technology was used to measure metabolic changes, and a luminescence assay was used to measure ROS release. RNA sequencing was performed on BIX‐01294‐treated monocytes ex vivo.

Results

The expression of EHMT2 mRNA and protein decreased in monocytes during induction of trained immunity. G9a inhibition by BIX‐01294 induced trained immunity and amplified trained immunity responses evoked by various microbial ligands in vitro. This was accompanied by decreased H3K9me2 at the promoters of pro‐inflammatory genes. G9a inhibition was also associated with amplified ex vivo trained immunity responses in circulating monocytes of NMIBC patients. Additionally, altered RNA expression of inflammatory genes in monocytes of NMIBC patients was observed upon ex vivo G9a inhibition. Furthermore, intravesical BCG therapy decreased H3K9me2 at the promoter of pro‐inflammatory genes.

Conclusion

Inhibition of G9a is important in the induction of trained immunity, and G9a may represent a novel therapeutic target in NMIBC patients.

Correction to: Rewiring of glucose metabolism defines trained immunity induced by oxidized low-density lipoprotein

The correct name of the 17th Author is presented in this paper.

The role of Toll-like receptor 10 in modulation of trained immunity

Toll‐like receptor 10 (TLR10) is the only member of the human Toll‐like receptor family with an inhibitory function on the induction of innate immune responses and inflammation. However, its role in the modulation of trained immunity (innate immune memory) is unknown. In the present study, we assessed whether TLR10 modulates the induction of trained immunity induced by β‐glucan or bacillus Calmette–Guérin (BCG). Interleukin 10 receptor antagonist production was increased upon activation of TLR10 ex vivo after BCG vaccination, and TLR10 protein expression on monocytes was increased after BCG vaccination, whereas anti‐TLR10 antibodies did not significantly modulate β‐glucan or BCG‐induced trained immunity in vitro. A known immunomodulatory TLR10 missense single‐nucleotide polymorphism (rs11096957) influenced trained immunity responses by β‐glucan or BCG in vitro. However, the in vivo induction of trained immunity by BCG vaccination was not influenced by TLR10 polymorphisms. In conclusion, TLR10 has a limited, non‐essential impact on the induction of trained immunity in humans.